1. Field of the Invention
The present invention relates generally to a vehicle service tool, and more particularly to an end piece of wheel cylinder piston adjustor.
2. Description of the Related Art
It is known that the disc brake of a vehicle includes two brake discs rotatable with the wheels. A brake calipers is used to clamp the brake discs so as to brake the wheel. The rotational speed of the brake discs is slowed down so as to slow down the vehicle or stop the vehicle. Substantially, the brake main cylinder provides fluid pressure through a pipeline to the wheel cylinder of the brake calipers. The piston of the wheel cylinder is axially moved to push the linings connected with the piston. At this time, the linings tightly abut against the faces of the brake discs to apply a frictional force against the move of the brake discs. Under such circumstance, the rotational speed of the wheel is reduced so as to slow down or stop the vehicle.
The braking effect of the disc brake is achieved by means of the frictional force between the linings and the brake discs. Therefore, the wear of the linings is inevitable. After a period of use, the worn linings must be replaced so as to ensure that the brake calipers can provide reliable braking effect to keep safety. In order to facilitate the replacement of the brake linings, various special tools are applicable to different types of brake calipers to help an operator to push the wheel cylinder piston back into the piston room for replacing the worn linings with new ones.
FIG. 1 shows a conventional disc-shaped end piece 1 as a component of the conventional wheel cylinder piston adjustor. The end piece 1 is formed with a central quadrangular hole 2. A drive end of the wheel cylinder piston adjustor is coaxially fitted in the quadrangular hole 2. Locating bolts 3 protruding from one face of the end piece 1 are engaged with the end of the wheel cylinder piston. The locating bolts 3 are positioned between the drive end of the wheel cylinder piston adjustor and the wheel cylinder piston. The conventional wheel cylinder piston adjustor is operated to apply a force to the wheel cylinder piston via the end piece 1 so as to push the wheel cylinder piston back into the piston room.
The end piece 1 has an annular base disc 4 formed with the central quadrangular hole 2. The drive end of the wheel cylinder piston adjustor is coaxially fitted in the quadrangular hole 2. A rotary disc 5 is attached to and connected with the base disc 4. One end of the locating bolts 3 is respectively slidable disposed in the arched slide slots 6 of the rotary disc 5. The other end of the locating bolts 3 is passed through the straight guide slots 7 of the base disc 4. Accordingly, when the rotary disc 5 and the base disc 4 are relatively rotated in the same axial direction, the arched slide slots 6 will drive the locating bolts 3 to move within the guide slots 7 so as to change the distance between the locating bolts 3. In this case, the end piece 1 is applicable to different wheel cylinder pistons with different sizes.
According to the above arrangement, the adjustment of the distance between the locating bolts 3 is achieved by means of the slide of one end of the locating bolts 3 within the corresponding slide slots 6. In this case, after a period of use, the locating bolts 3 and the slide slots 6 are likely to wear due to relative sliding. As a result, the locating bolts 3 are likely to clog and can be hardly smoothly slid. Therefore, in practice, the conventional end piece 1 cannot be conveniently used and needs to be improved.